Pre-fulling dimensions (inches): 2.25 wide x 4 long x 2.5 tall
Post-fulling dimensions (inches): 2.25 wide x 4 long x 1.75 tall
Total fulling time: 20 min (including washing out the sink before and after)

I did this in the sink, as a) I’m a control freak like that and b) I couldn’t be bothered to deal with the washer for something this small. I’m really glad I did, however, as I have no idea how you’d get a square box out of the washer -- the sides stretched a lot while I was working and at times it looked more like a disc than a box. I ended up doing quite a bit of work on the sides to force them to felt inwards and to shape the edges. If I were to do it again, I’d likely knit so I had a row of purl bumps along all the edges to make them easier to keep track of as well.